1. Field
Methods and apparatuses consistent with exemplary embodiments relate to video encoding and decoding.
2. Description of Related Art
In general, according to video compression standards, such as Moving Picture Expert Group (MPEG) and H.26X, a bitstream is generated by compressing image data through prediction, transformation, quantization, and entropy encoding processes.
In the prediction process, a prediction image of image data to be encoded is generated by performing intra prediction using spatial correlations of images, or inter prediction using temporal correlations of images.
In the transformation process, an error data, which is a difference between an original image and the prediction image generated in the prediction process, is transformed to the transformation domain by using various transformation methods. Representative transformation methods include discrete cosine transformation (DCT) and wavelet transformation.
In the quantization process, transformation coefficients generated in the transformation process are appropriately loss-compressed according to the error value and the size of a target bitstream. Most standard image and video codecs based on lossy compression perform quantization and inverse quantization processes according to a quantization step. In the quantization process, a quantized value is obtained by dividing an input value by the quantization step and then rounding off the divided value to an integer. Due to the quantization process, information is loss-compressed. Because all lossy compression technologies include a quantization process, original data may not be perfectly restored but a compression rate may be increased.